TW202128277A - Catalyst and its use in ethylbenzene dealkylation - Google Patents

Abstract

An ethylbenzene dealkylation catalyst composition comprising a ZSM-5 type zeolite as a carrier component, wherein said zeolite has been synthesized from an aqueous reaction mixture comprising one or more alumina sources, one or more silica sources, one or more alkali sources, and one or more primary and/or secondary amines and wherein the ZSM-5 type zeolite has a number average crystallite size in the range of from 1 to 10 [mu]m and a molar silica-to-alumina ratio (SAR) in the range of from 30 to 70; a method for reducing xylene losses in an ethylbenzene dealkylation process, said method comprising conducting the ethylbenzene dealklylation process in the presence of the afore-mentioned catalyst composition; and a process for the dealkylation of ethylbenzene, which process comprises contacting, in the presence of hydrogen, a feedstock which comprises ethylbenzene with said catalyst composition.

Description

Catalyst and its use in ethylbenzene dealkylation

The present invention relates to a catalyst composition containing ZSM-5 zeolite and its use in ethylbenzene dealkylation.

Ethylbenzene is one of the aromatic hydrocarbons obtained from light oil pyrolysis or reconstituted oil. Reconstituted oil is an aromatic product given by the catalytic conversion of straight-run hydrocarbons boiling in the range of 70 to 190°C, such as straight-run light oil. The catalyst used to produce reconstituted oil is usually a platinum-on-alumina catalyst supported on alumina. When converted to reconstituted oil, the aromatic hydrocarbon content increases significantly, and the resulting hydrocarbon mixture becomes extremely desirable as a source of valuable chemical intermediates and as a component of gasoline. The main components are a group of aromatic hydrocarbons commonly called BTX: benzene, toluene and xylene, and ethylbenzene. Other components may be present, such as its hydrogenated homologues, for example cyclohexane.

In the BTX group, the most valuable components are benzene and xylene, so BTX is often processed to increase the ratio of the two aromatic hydrocarbons: toluene is hydrodealkylated to benzene and toluene is disproportionated to benzene and xylene. Among xylenes, p-xylene is the most useful commodity, and xylene isomerization or transalkylation methods have been developed to increase the ratio of p-xylene.

Another method that can be applied is the hydrodealkylation of ethylbenzene to benzene.

Generally, it is preferable to separate BTX from the reformed oil stream, and then separate the C ₈ aromatics by distillation, and then extract para-xylene via selective adsorption or crystallization. Then the paraxylene depleted C ₈ aromatics stream xylene isomerization, p-xylene and its object is to make the components can be recycled to maximize the flow and extracted more p-xylene. To avoid the accumulation of ethylbenzene in the recycle stream, the ethylbenzene must be converted. Usually, this is done by dealkylating ethylbenzene to produce valuable benzene or by recombining ethylbenzene into xylene to increase the xylene yield. In practice, the catalyst system is used to isomerize xylene to equilibrium while simultaneously recombining ethylbenzene into xylene or dealkylating ethylbenzene. The latter method is the subject of the present invention.

In the dealkylation of ethylbenzene, the main problem is not only to ensure a high degree of conversion of ethylbenzene to benzene and make the xylene isomerization close to equilibrium, but also to avoid the loss of xylene.

Xylene may generally be lost due to, for example, transalkylation between benzene and xylene to form toluene, or by adding hydrogen to form, for example, olefins or alkanes. Another way of xylene loss is the disproportionation of two xylene molecules, which leads to the formation of trimethylbenzene (TMB) and toluene, which are significantly less valuable.

Therefore, the object of the present invention is to provide a catalyst that will convert ethylbenzene to benzene with reduced xylene loss and, in particular, reduced TMB formation.

In order to convert the BTX stream to increase the proportion of tightly configured molecules, extensive proposals have been made to utilize zeolite catalysts. One common zeolite group used in ethylbenzene dealkylation is MFI zeolite, and in particular, ZSM-5. ZSM-5 zeolite is well known and documented in the art.

Many preparation methods of active MFI zeolite including ZSM-5 have been proposed. See, for example, US 3,702,886 A. The reference content is provided in Atlas, or Database, of Zeolite Structures and provided in Such as Yu et al. "Microporous and Mesoporous Materials (Microporous and Mesoporous Materials)" 95 (2006) pages 234 to 240 and Iwayama et al. in other literature references in US 4,511,547 A.

US 3,702,886 A uses a silica source, an alumina source, and an alkali source to prepare zeolite, and describes the use of tetraalkylammonium cations such as tetrapropylammonium (TPA) cations as organic structure directing agents in the preparation of ZSM-5.

US 8,574,542 B2 describes the preparation of ZSM-5 by synthesis from an aqueous reaction mixture containing an alumina source, a silica source, an alkali source and L-tartaric acid or its water-soluble salt, and the ZSM-5 is used for conversion In the process containing aromatic hydrocarbon feedstock, in particular, it is used in the process of selective dealkylation of ethylbenzene.

US 4312790 A discloses a method for preparing a precious metal-containing zeolite catalyst for aromatics treatment, in particular, xylene isomerization. The method comprises combining the noble metal in cationic form with the zeolite after crystallization, before the formation of the final catalyst particles, and before any calcination or steaming of the zeolite, the zeolite being characterized in that the molar ratio of silica to alumina is At least 12 and the constraint index is roughly in the range of 1-12. Example 5 in US 4312790 A describes the use of alumina binder to prepare Pt-ZSM-5 catalyst. The ZSM-5 zeolite in Example 5 was prepared using a mixture containing tetrapropylammonium bromide (TPA) as a structure directing agent. The structure directing agent is formed in situ using a solution containing n-bromopropane and tri-n-propylamine. Before extruding the Pt-ZSM-5/Al ₂ O ₃ catalyst particles, the zeolite was mixed with an alumina binder and impregnated with platinum.

WO 2011/143031 A2 discloses a process for dealkylating ethylbenzene, which comprises passing a stream containing ethylbenzene through an effective amount of a catalyst, wherein the catalyst comprises (a) a molecular sieve containing one or more crystals, wherein the molecular sieve Have an external surface area not exceeding 20 m ² /g; and (b) adhesives. Preferably, the outer surface area of the molecular sieve does not exceed 12 m ² /g, and more preferably does not exceed 8 m ² /g. In WO 2011/143031 A2, the molecular sieve may be MFI zeolite.

The example in WO 2011/143031 A2 describes the use of sodium aluminate, silica and n-butylamine as templates to prepare MFI zeolite. The prepared zeolite has larger crystals (> 10 μm) and a high molar ratio (SAR) of silica to alumina of> 75 or smaller crystals (< 1 μm) and a low SAR of <60.

It has been found in the present invention that ZSM-5 crystals are prepared by producing a certain molar ratio (SAR) of silica and alumina and number-average crystallite size, and also using certain compounds as structure-directing agents. It is possible to prepare a catalyst composition that provides a significant reduction in xylene loss in the dealkylation of ethylbenzene.

Therefore, the present invention provides an ethylbenzene dealkylation catalyst composition comprising ZSM-5 type zeolite as a support component, wherein the zeolite is composed of one or more alumina sources, one or more silica sources, and one or more alkalis. Synthesis of an aqueous reaction mixture of a source and one or more primary and/or secondary amines, and wherein the ZSM-5 type zeolite has a number average crystallite size in the range of 1 to 10 µm and silica in the range of 30 to 70 Compared with alumina (SAR).

The present invention further provides a method for reducing the loss of xylene in the ethylbenzene dealkylation process, the method comprising performing the ethylbenzene dealkylation process in the presence of the above-mentioned catalyst composition.

The present invention also provides a process for the dealkylation of ethylbenzene, which comprises contacting a raw material containing ethylbenzene with the catalyst composition in the presence of hydrogen.

It has been unexpectedly discovered that the ZSM-5 type zeolite prepared as described herein provides a greatly reduced xylene loss compared to the ZSM-5 type zeolite prepared using other structure directing agents such as tetrapropylammonium (TPA) compounds. In particular, it has been found that when used for ethylbenzene dealkylation, a catalyst composition comprising a ZSM-5 type zeolite prepared as described herein and having characteristics as described herein produces lower TMB formation. In addition, it has also been found that these catalysts exhibit unexpected additional advantages when surface modification treatment is also performed on the carrier therein.

In the characterization of zeolite, the molar ratio of silica to alumina (SiO ₂ /Al ₂ O ₃ , "SAR" in this article) is usually an important parameter. This parameter is inversely proportional to the density of acid sites, which is related to the presence of aluminum in the framework of crystalline aluminosilicate zeolite. Conventionally, the SAR of crystalline aluminosilicate zeolite materials is determined by global element analysis.

The ZSM-5 zeolite in the present invention has a mole of silica and alumina in the range of 30 to 70, preferably in the range of 45 to 70, more preferably in the range of 45 to 65, and even more preferably in the range of 45 to 60 Ratio (SAR). This (whole or total) SAR can be determined by any of a variety of chemical analysis techniques. These technologies include X-ray fluorescence, atomic adsorption and inductively coupled plasma atomic emission spectrometry (ICP-AES). All will provide roughly the same overall ratio. The molar ratio of silica and alumina used in the present invention is preferably determined by X-ray fluorescence.

The ZSM-5 type zeolite in the present invention can have various particle sizes. The zeolite has a number average particle size in the range of 1 to 10 µm (micrometers) (hereinafter referred to as "crystallite size"). The number average crystallite size of ZSM-5 type zeolite is preferably in the range of 1 to 7 µm, more preferably in the range of 1 to 5 µm. As used herein, the "crystallite size" is measured by scanning electron microscopy (SEM), and the average value is calculated as the number average.

In a preferred embodiment of the present invention, the ZSM-5 zeolite has a molar ratio (SAR) and number average of silica and alumina in the range of 30 to 70 selected from one of the following preferred combinations Crystallite size:-(i) SAR in the range of 30 to 70 and number average crystallite size in the range of 1 to 7 µm; (ii) SAR in the range of 30 to 70 and number average in the range of 1 to 5 µm Crystal size.

In another preferred embodiment of the present invention, the ZSM-5 zeolite has a molar ratio (SAR) and number of silica and alumina in the range of 45 to 70 selected from one of the following preferred combinations. Average crystallite size:-(i) SAR in the range of 45 to 70 and number average crystallite size in the range of 1 to 10 µm; (ii) SAR in the range of 45 to 70 and number average in the range of 1 to 7 µm Crystallite size; (iii) SAR in the range of 45 to 70 and number average crystallite size in the range of 1 to 5 µm.

In another preferred embodiment of the present invention, the ZSM-5 zeolite has a molar ratio (SAR) and number of silica and alumina in the range of 45 to 65 selected from one of the following preferred combinations. Average crystallite size:-(i) SAR in the range of 45 to 65 and number average crystallite size in the range of 1 to 10 µm; (ii) SAR in the range of 45 to 65 and number average in the range of 1 to 7 µm Crystallite size; (iii) SAR in the range of 45 to 65 and number average crystallite size in the range of 1 to 5 µm.

In another preferred embodiment of the present invention, the ZSM-5 zeolite has a molar ratio (SAR) and number of silica and alumina in the range of 45 to 60 selected from one of the following preferred combinations. Average crystallite size:-(i) SAR in the range of 45 to 60 and number average crystallite size in the range of 1 to 10 µm; (ii) SAR in the range of 45 to 60 and number average in the range of 1 to 7 µm Crystallite size; (iii) SAR in the range of 45 to 60 and number average crystallite size in the range of 1 to 5 µm.

As measured by ASTM D4365-95, the ZSM-5 type zeolite used in the ethylbenzene dealkylation catalyst composition of the present invention preferably has more than 350 m ² /g, more preferably more than 375 m ² /g, and most preferably The total surface area is greater than 400 m ^{2 /g.}

The ZSM-5 type zeolite used in the ethylbenzene dealkylation catalyst composition of the present invention is composed of one or more alumina sources, one or more silica sources, one or more alkali sources and one or more primary and/or secondary Synthesis of aqueous reaction mixture of grade amine.

In the present invention, one or more sources of silica are preferably selected from silica sol, silica gel, silica aerogel, silica hydrogel, silicic acid, silicate and silicic acid sodium.

As the alumina source, known alumina sources that have been used to prepare zeolite so far can be used, such as sodium aluminate, aluminum sulfate, aluminum nitrate, alumina sol, alumina gel, activated alumina, γ-alumina, and α-Alumina.

Examples of alkali sources are sodium hydroxide and potassium hydroxide, with sodium hydroxide being preferred. It should be understood that if sodium silicate is used as a source of silicon dioxide and sodium aluminate is used as a source of alumina, both compounds will also serve as a source of alkalinity.

In a particularly preferred embodiment of the present invention, the one or more amines are primary and/or secondary amines ^{having the formula R 1} NH ₂ and/or R ² R ^{3 NH, wherein one of R 1} , R ² , and R ³ Each is independently selected from alkyl groups having 3 to 8 carbon atoms, and wherein R ² and R ³ may be the same or different. Examples of preferred amines include propylamine, n-butylamine, n-pentylamine, n-hexylamine, n-heptylamine, n-octylamine, dipropylamine, and diisopropylamine.

More specifically, the one or more amines are primary and/or secondary amines ^{having the formula R 1} NH ₂ and/or R ² R ^{3 NH, wherein each of R 1} , R ² , and R ³ is independently selected It is a straight chain alkyl group having 3 to 8 carbon atoms, more preferably 4 to 8 carbon atoms, and wherein R ² and R ³ may be the same or the same. Examples of preferred linear alkylamines include n-butylamine, n-pentylamine, n-hexylamine, n-heptylamine, and n-octylamine.

In addition to the ZSM-5 type zeolite as described above, the catalyst composition according to the present invention preferably further includes one or more metals and one or more inorganic oxide binders.

In the catalyst composition of the present invention, ZSM-5 zeolite can exist in various forms according to the ions present at the cationic site in the zeolite structure. Generally, the usable form contains alkali metal ions, alkaline earth metal ions, or hydrogen or hydrogen precursor ions at the cation site. In the catalyst composition of the present invention, the zeolite usually exists in a form containing hydrogen or a hydrogen precursor; this form is usually referred to as the H ⁺ form. Zeolite can be used in template-free or template-containing form.

The inorganic oxide binder is preferably a refractory oxide selected from the group consisting of silicon dioxide, zirconium dioxide and titanium dioxide.

Optimally, silica is used as the binder in the catalyst composition of the present invention, and it can be naturally occurring silica or can be in the form of a gel-like precipitate, sol or gel. The form of silicon dioxide is not limited and silicon dioxide can take any of its various forms: crystalline silicon dioxide, glassy silicon dioxide or amorphous silicon dioxide. The term amorphous silica covers the wet type of pyrolysis or vapor phase silica, which includes precipitated silica and silica gel. Silica sol or colloidal silica is a non-settling dispersion of amorphous silica in a liquid, usually water, usually stabilized by anionic, cationic or nonionic materials.

The silica binder is preferably a mixture of two types of silica, and most preferably a mixture of powdered silica and silica sol. Silicon dioxide in powder form preferably has a ^{surface area in the range of 50 to 1000 m 2} /g; and, as measured by ASTM C 690-1992 or ISO 8130-1, in the range of 2 to 200 µm, preferably 2 to 100 µm, More preferably, the average particle size is in the range of 2 to 60 µm, especially 2 to 10 µm. An extremely suitable powder form of silicon dioxide material is "Sipernat 50", a white silicon dioxide powder with mainly spherical particles obtained from Evonik ("Sipernat" is a brand name). An extremely suitable silica sol is the silica sol sold by Nouryon under the brand name "Bindzil". When the mixture contains powdered silica and silica sol, the two components can be 1:1 to 10:1, preferably 2:1 to 5:1, and more preferably 2:1 to 3:1 The weight ratio of powder form to sol within the range exists. The binder can also consist essentially of silica only in powder form.

When silicon dioxide in powder form is used as the binder in the catalyst composition of the present invention, it is preferable to use the form of small particles, as measured by ASTM C 690-1992, which has a range of 2 to 10 µm Average particle size. With these materials, additional improvements in the strength of the carrier can be found. An extremely suitable small particle form is the one obtained from Evonik under the brand name "Sipernat 500LS".

The silicon dioxide component used can be pure silicon dioxide and not used as a component in another inorganic oxide. For some embodiments, the silicon dioxide and the actual carrier are substantially free of any other inorganic oxide binder materials, and especially free of alumina. Depending on the circumstances, there may be up to 2 wt% alumina based on the total support.

The carrier in the catalyst composition of the present invention can be regarded as a composite containing ZSM-5 type zeolite and an inorganic oxide binder. Based on the total weight of the carrier composition, the carrier preferably contains a binder in the range of 20 to 75 wt% in combination with a ZSM-5 zeolite in the range of 25 to 80 wt%, more preferably 35 to 80 wt% ZSM-5 zeolite combination in the range of 20 to 65 wt% of the binder, more specifically, the ZSM-5 zeolite combination in the range of 25 to 60 wt% The binder, even more specifically, the binder in the range of 25 to 55 wt% in combination with the ZSM-5 zeolite in the range of 45 to 75 wt%, and most specifically, the binder in the range of 50 to 70 wt% The binder in the range of 30 to 50 wt% of the ZSM-5 zeolite combination. The binder is preferably silica.

In addition to the aforementioned ZSM-5 type zeolite, the support and the resulting catalyst composition may contain one or more other zeolites. Preferably other zeolites can be selected from the group consisting of: (others) ZSM-5, ZSM-11, ZSM-12, EU-1, ZSM-57, ZSM-22, ZSM-23, ITQ-1, PSH-3 , Stilbite, TNU-10, TS-1 and Mordenite. Most preferably, the additional zeolite is selected from the group consisting of ZSM-11, ZSM-12, EU-1 and mordenite. Preferably, based on the total weight of the carrier, one or more other zeolites are in an amount in the range of 0 to 35 wt%, more preferably in an amount in the range of 1 to 20 wt%, more preferably 2 to 10 wt% An amount within the range is present in the carrier.

In another embodiment, the present invention provides a method for preparing the above-mentioned ethylbenzene dealkylation catalyst composition, the method comprising:- (I) Preparation of ZSM-5 zeolite as a carrier component from an aqueous reaction mixture containing one or more alumina sources, one or more silica sources, one or more alkali sources, and one or more primary and/or secondary amines ； (Ii) preparing a support comprising the ZSM-5 type zeolite and one or more inorganic oxide binders; and (iii) depositing one or more metals on the support.

The mixture of ZSM-5 zeolite and inorganic oxide binder can be shaped into any suitable form such as powder, extrudate, pellets and granules. It is preferably formed by extrusion. To prepare extrudates, usually zeolite will be combined with a binder, preferably silica, and if necessary, with a peptizer, and mixed to form a sticky or thick paste. The peptizer can be any material that will change the pH of the mixture sufficiently to induce the solid particles to de-agglomerate. Peptizers are well-known and cover organic acids and inorganic acids such as nitric acid, and alkali metal hydroxides such as ammonia, ammonium hydroxide, preferably sodium hydroxide and potassium hydroxide, alkaline earth metal hydroxides, and, for example, methylamine Alkaline material of organic amine and ethylamine. Ammonia is a preferred peptizer and can be provided in any suitable form, for example via an ammonia precursor. Examples of ammonia precursors are ammonium hydroxide and urea. Ammonia may also be present as part of the silica component, especially when silica sol is used, but additional ammonia may still be needed to impart an appropriate pH change. It has been found that the amount of ammonia present during extrusion affects the pore structure of the extrudate, which can provide advantageous properties. Suitably, the amount of ammonia present during extrusion may be in the range of 0 to 5 wt%, preferably 0 to 3 wt%, more preferably 0 to 1.9 wt%, based on the total dry mixture.

The support is preferably a shaped support, and can be treated to enhance the activity of the ZSM-5 type zeolite component. In fact, in a specific embodiment of the present invention, it has been unexpectedly found that the catalyst composition of the present invention exhibits additional performance benefits when the support therein is also subjected to surface modification treatment.

Therefore, in certain embodiments, the support containing the above-mentioned ZSM-5 type zeolite may be subjected to surface modification treatment before being impregnated with one or more metals to prepare the catalyst composition of the present invention.

Therefore, the present invention also provides a method for preparing the above-mentioned ethylbenzene dealkylation catalyst composition, the method comprising:- (I) Preparation of ZSM-5 zeolite as a carrier component from an aqueous reaction mixture containing one or more alumina sources, one or more silica sources, one or more alkali sources, and one or more primary and/or secondary amines ； (Ii) Preparation of a carrier containing the ZSM-5 type zeolite and one or more inorganic oxide binders; (Iii) Surface modification treatment of ZSM-5 zeolite; and (Iv) Depositing one or more metals on the carrier.

The surface modification of zeolite reduces the molar percentage of alumina, which basically implies a reduction in the number of acidic sites. This can be achieved in various ways. The first method is to coat the low-acid inorganic refractory oxide coating on the surface of the crystallites of the ZSM-5 zeolite.

Another extremely suitable way to modify the surface of ZSM-5 zeolite is to dealuminate it, such as the dealumination described in US 6,949,181 B2.

The ZSM-5 type zeolite may be subjected to a surface modification treatment before being incorporated into the carrier, or the ZSM-5 type zeolite may be subjected to a surface modification treatment after being incorporated into the carrier.

In the present invention, it has been found that it is particularly advantageous to dealumulate a support containing ZSM-5 type zeolite as a support component.

Therefore, preferably, the surface modification treatment in the above method for preparing the above-mentioned ethylbenzene dealkylation catalyst composition includes dealumination treatment on the support before or after depositing one or more metals. Preferably, the support is dealuminated before depositing one or more metals.

Compared with the corresponding ZSM-5 zeolite that has not been dealuminated, the dealumed ZSM-5 zeolite will have a lower alumina concentration on the surface. The zeolite itself or the zeolite that has been incorporated into the support extrudate can be dealuminated. In many cases, it is preferred to dealumulate the support extrudate. The carrier extrusion can be performed before or after depositing one or more metals.

Generally, dealumination of the crystallites of molecular sieves such as zeolite refers to a process in which aluminum atoms are extracted from the molecular sieve framework to leave defects, or are extracted and replaced with other atoms such as silicon, titanium, boron, germanium or zirconium. The removal of alumina from the zeolite can be carried out in any manner known to those skilled in the art.

Examples of dealumination treatments include steaming, treatment with F-containing salts, and treatment with acids such as hydrochloric acid (HCl), nitric acid (HNO ₃ ) or ethylenediaminetetraacetic acid (EDTA).

In US 5,242,676 A, an extremely suitable method for dealumination of the surface of zeolite crystallites is disclosed. Another method for obtaining a zeolite with a dealuminated outer surface is disclosed in US 4,088,605 A.

In one embodiment of the present invention, it is preferable to treat ZSM-5 zeolite particles or carrier extrudates at a temperature higher than 300° C. in the presence of steam by a steaming method including heat treatment in order to remove oxidation from the zeolite framework. aluminum. The degree of dealumination depends on the steam concentration and temperature. In a preferred embodiment, the temperature is in the range of 500 to 750°C, and the vapor concentration in the air is in the range of 10 to 25%.

In another embodiment of the present invention, it is preferable to treat the zeolite particles, which are combined with a binder as the carrier, with a fluorine-containing salt as the case may be. Most preferably, dealumination is carried out by the following method, in which a solution of zeolite and ammonium fluoride, more specifically, a compound selected from the group consisting of fluorosilicate and fluorotitanate, is best Contact with a compound selected from the group of fluorosilicates. These methods are described in more detail in US 4,753,910 A.

Most preferably, the dealumination method involves contacting the zeolite with a solution of fluorosilicate, wherein the fluorosilicate is represented by the following formula: (A) _2/b SiF ₆ where "A" is a value other ^{than H +} "B" Metal or non-metal cations. Examples of the cation "b" are alkylammonium, NH ₄ ⁺ , Mg ⁺⁺ , Li ⁺ , Na ⁺ , K ⁺ , Ba ⁺⁺ , Cd ⁺⁺ , Cu ⁺ , Ca ⁺⁺ , Cs ⁺ , Fe ⁺⁺ , Co ⁺⁺ , Pb ⁺⁺ , Mn ⁺⁺ , Rb ⁺ , Ag ⁺ , Sr ⁺⁺ , Tl ⁺ and Zn ⁺⁺ . Preferably, "A" is an ammonium cation.

The solution containing fluorosilicate is preferably an aqueous solution. The concentration of the salt is preferably at least 0.005 mol fluorosilicate/l, more preferably at least 0.007 mol fluorosilicate/l, most preferably at least 0.01 mol fluorosilicate/l. The concentration is preferably at most 0.5 mol fluorosilicate/l, more preferably at most 0.3 mol fluorosilicate/l, most preferably at most 0.1 mol fluorosilicate/l. Preferably, the weight ratio of fluorosilicate solution to zeolite is 50:1 to 1:4 in fluorosilicate solution:zeolite. If the zeolite is present with the binder, the binder is not taken into consideration for these weight ratios.

The pH of the fluorosilicate aqueous solution is preferably between 2 and 8, more preferably between 3 and 7.

The zeolite material is preferably contacted with the fluorosilicate solution for 0.5 to 20 hours, more specifically, for a period of 1 to 10 hours. The temperature is preferably 10 to 120°C, more specifically, 20 to 100°C. The amount of fluorosilicate is preferably at least 0.002 mol fluorosilicate/100 g total zeolite, more specifically, at least 0.003 mol fluorosilicate/100 g total zeolite, more specifically, at least 0.004 mol fluorosilicate/100 g total zeolite, more specifically, at least 0.005 mol fluorosilicate/100 g total zeolite. The amount is preferably at most 0.5 mol fluorosilicate/100 g total zeolite, more preferably at most 0.3 mol/100 g total zeolite, more preferably at most 0.1 mol fluorosilicate/100 g total zeolite. If the zeolite is present with the binder, the binder is not taken into consideration for these weight ratios.

In the (surface) dealumination method described above, the method involving treatment with hexafluorosilicate, most suitably ammonium hexafluorosilicate (AHS) as described in US 6,949,181 B2, is used to prepare the above-mentioned present The method of the inventive ethylbenzene dealkylation catalyst composition is the best. Preferably, the concentration of ammonium hexafluorosilicate (AHS) is in the range of 0.005 to 0.5 M. Preferably, the concentration is in the range of 0.01 to 0.2 M, more preferably 0.01 to 0.05 M and especially 0.01 to 0.03 M, which has been found to provide a favorable catalyst composition.

One or more of the metals in the catalyst composition of the present invention preferably include those selected from groups 6, 7, 8, 9, 10 and 14 of the periodic table (for example, in the IUPAC periodic table dated May 1, 2013 Defined). More preferably, one or more metals in the catalyst composition of the present invention are selected from those metals including chromium, ruthenium, rhenium, iron, chromium, molybdenum, tungsten, palladium, platinum, tin, lead, silver, copper and nickel .

Most preferably, the catalyst composition of the present invention contains platinum as the catalytically active metal. Optionally, the catalyst composition of the present invention includes platinum as the catalytically active metal and includes one or more additional metal promoters selected from tin, lead, copper, nickel, gallium, cerium, and silver.

Calculate the weight of one or more metals based on the total weight of the catalyst composition and regardless of the actual form of the metal.

The amount of the one or more metals in the catalyst composition depends on the nature of the metal used. For example, based on the total weight of the catalyst composition and regardless of the actual form of the metal, in the case of calculating the amount of the metal, the oxidation or sulfide hydrogenation metal (ie chromium, molybdenum, tungsten, and iron) can usually Use in amounts exceeding 1 wt%. In contrast, based on the total weight of the catalyst composition and regardless of the actual form of the metal, other metals (such as rhenium, ruthenium, platinum and palladium) should be less than The amount of 1 wt% is used.

In a preferred embodiment of the catalyst composition of the present invention, platinum is present as the catalytically active metal in an amount ranging from 0.001 to 0.1 wt% based on the total weight of the catalyst composition. Most suitably, platinum is present as the catalytically active metal in an amount ranging from 0.01 to 0.1 wt%, preferably 0.01 to 0.05 wt%, based on the total weight of the catalyst composition.

Optionally, based on the total weight of the catalyst composition, in addition to platinum, one or more additional metals selected from tin, lead, copper, nickel and silver are present in the catalyst composition in individual amounts less than 1 wt%. Based on the total weight of the catalyst composition, one or more additional metals are selected as appropriate. The individual amount is most suitably in the range of 0.0001 to 0.5 wt%, preferably in the range of 0.01 to 0.5 wt%, more preferably 0.1 Exist in an amount within the range of 0.5 wt%. If tin or lead is an additional metal, it is present in an amount ranging from 0.01 to 0.5 wt% based on the total catalyst. Based on the total weight of the catalyst composition, it is most suitably present at 0.1 to 0.5 wt%, preferably 0.2 to Exist in an amount within the range of 0.5 wt%.

The catalyst composition of the present invention can be prepared using standard techniques for the following: combining ZSM-5 type zeolite, binder and other support components as appropriate; forming as appropriate; impregnating with one or more catalytically active metal compounds; And any subsequent applicable method steps, such as forming (if not done before impregnation), drying, calcination and reduction.

The metal can be placed on the formed carrier by a method commonly used in the art. The metal can be deposited on the carrier material before forming, but it is preferred to deposit the metal on the shaped carrier.

Preferably, the resulting extrudate is subjected to a calcination step before the metal is placed, which is preferably carried out at a temperature higher than 500°C and usually higher than 600°C.

The pore volume impregnation of the metal from the metal salt solution is an extremely suitable method for placing the metal on a shaped support. The metal salt solution may have a pH in the range of 1-12. The platinum salts that can be used conveniently are chloroplatinate and ammonium-stable platinum salt. Additional silver, nickel or copper metal salts can be added to the solution in the form of water-soluble organic or inorganic salts. Examples of suitable salts are nitrates, sulfates, hydroxides and ammonium (amine) complexes. Examples of suitable tin salts that can be used are stannous (II) chloride, stannous (IV) chloride, stannous sulfate, and stannous acetate. Examples of suitable lead salts are lead acetate, lead nitrate and lead sulfate.

When more than one metal is present in the catalyst composition of the present invention, the metals can be impregnated sequentially or simultaneously. Preferably, the metal is added at the same time. When using simultaneous impregnation, the metal salt used must be compatible and not hinder metal deposition.

After the support is shaped and also after impregnation of one or more metals, the support/catalyst composition is suitably dried and calcined. The drying temperature is suitably 50 to 200°C; the drying time is suitably 0.5 to 5 hours. The calcination temperature is extremely suitably in the range of 200 to 800°C, preferably 300 to 600°C, and most preferably, the calcination temperature is 400 to 475°C. For the calcination of the carrier, a relatively short period of time is required, for example, 0.5 to 3 hours. For the calcination of the catalyst composition, it may be necessary to use a controllable temperature that is slowly increased at a low heating rate to ensure the best dispersion of the metal: this calcination may take 5 to 20 hours.

Before use, it is usually necessary to ensure that any hydrogenation metal in the catalyst composition is in metallic (not oxidized) form. Therefore, the catalyst composition of the present invention is subjected to, for example, heating in a reducing atmosphere, such as hydrogen diluted with an inert gas or an inert gas mixture such as nitrogen and carbon dioxide, at a temperature in the range of 150 to 600°C for 0.5 to A reduction condition of 5 hours is useful.

The catalyst composition of the present invention is particularly suitable for the selective dealkylation of ethylbenzene.

Ethylbenzene feedstock is most suitably derived from a recombination unit or a light oil pyrolysis unit or the effluent of a xylene isomerization or transalkylation unit. After distillation and p-xylene extraction, the raw material usually contains C ₇ to C ₉ hydrocarbons, and in particular, in addition to ethylbenzene, it also contains one or more of o-xylene, meta-xylene, and p-xylene. Generally, the amount of ethylbenzene in the raw material is in the range of 0.1 to 50 wt%, and the total xylene content is usually at least 20 wt%. Generally, xylene will not be in a state of thermodynamic equilibrium, and the content of p-xylene will therefore be lower than that of other isomers.

The raw material is contacted with the catalyst composition of the present invention in the presence of hydrogen. This can be done in a fixed bed system. This system can be operated continuously or in batches. It is preferably operated continuously in a fixed bed system. The catalyst can be used in one reactor or in several separate reactors connected in series or operated in a swing system to ensure continuous operation during catalyst replacement.

The dealkylation method is suitably carried out at a temperature in the range of 300 to 500°C, a pressure in the range of 0.1 to 50 bar (10 to 5,000 kPa), and a liquid space velocity in the range of ^{0.5 to 20 hours-1.} Normally a hydrogen partial pressure in the range of 0.05 to 30 bar (5 to 3,000 kPa) is used. The molar ratio of hydrogen to feed is in the range of 0.5 to 100, usually 1 to 10 mol/mol.

The following examples illustrate the invention. Instance Zeolite preparation Zeolite A (comparison)

536 grams of colloidal silica (Nyacol, 40 wt% SiO ₂ ), 25.4 grams of sodium aluminate (43 wt% solution), 28.5 grams of tetrapropylammonium bromide (TPA) (50 wt% solution), 7.8 grams of chlorinated Tetramethylammonium (TMA) solution (50 wt% solution), 3.1 g sodium hydroxide (50 wt% solution) and 353 g water are mixed together. The gel crystallized at 170°C for 24 hours.

The crystalline product was filtered, washed with deionized water and dried in air. The zeolite powder was calcined at 550°C for 6 hours to remove organic molecules from the pores. The product was analyzed by powder XRD and showed pure phase ZSM-5 (MFI). The zeolite has a SAR of 62. The crystal size was analyzed by SEM and the average crystal size showed 2.3 microns. Zeolite B (comparison)

Combine 780 grams of colloidal silica (Nyacol, 40 wt% SiO ₂ ), 44.4 grams of sodium aluminate (43 wt% solution), 41.5 grams of tetrapropylammonium bromide (TPA) (50 wt% solution), and 1 gram of hydroxide Sodium (50 wt% solution) and 517 grams of water are mixed together. The gel crystallized at 180°C for 18 hours.

The crystalline product was filtered, washed with deionized water and dried in air. The zeolite powder was calcined at 550°C for 6 hours to remove organic molecules from the pores.

The product was analyzed by powder XRD and showed pure phase ZSM-5 (MFI). The zeolite has a SAR of 51. The crystal size was analyzed by SEM and the average crystal size showed 0.8 microns. Zeolite C

Mix 687 g colloidal silica (Nyacol, 40 wt% SiO ₂ ), 35.5 g sodium aluminate (43 wt% solution), 16.9 g 1-butylamine, 17.1 g sodium hydroxide (50 wt% solution), and 641 g The water is mixed together. The gel crystallized at 180°C for 18 hours.

The crystalline product was filtered, washed with deionized water and dried in air. The zeolite powder was calcined at 550°C for 6 hours to remove organic molecules from the pores.

The product was analyzed by powder XRD and showed pure phase ZSM-5 (MFI). The zeolite has a SAR of 55. The crystal size was analyzed by SEM and the average crystal size showed 2.9 microns. Zeolite D

Combine 715 g colloidal silica (Nyacol, 40 wt% SiO ₂ ), 36.9 g sodium aluminate (43 wt% solution), 20.7 g 1-pentylamine, 17.8 g sodium hydroxide (50 wt% solution), and 667 g The water is mixed together. The gel crystallized at 180°C for 18 hours.

The crystalline product was filtered, washed with deionized water and dried in air. The zeolite powder was calcined at 550°C for 6 hours to remove organic molecules from the pores.

The product was analyzed by powder XRD and showed pure phase ZSM-5 (MFI). The zeolite has a SAR of 50. The crystal size was analyzed by SEM and the average crystal size showed 2.3 microns. Zeolite E

Combine 700 g colloidal silica (Nyacol, 40 wt% SiO ₂ ), 36.2 g sodium aluminate (43 wt% solution), 23.6 g 1-hexylamine, 17.4 g sodium hydroxide (50 wt% solution), and 653 g The water is mixed together. The gel crystallized at 180°C for 18 hours.

The crystalline product was filtered, washed with deionized water and dried in air. The zeolite powder was calcined at 550°C for 6 hours to remove organic molecules from the pores.

The product was analyzed by powder XRD and showed pure phase ZSM-5 (MFI). The zeolite has a SAR of 49. The crystal size was analyzed by SEM and the average crystal size was shown to be 3.8 microns. Zeolite F

Mix 720 grams of colloidal silica (Nyacol, 40 wt% SiO ₂ ), 37.2 grams of sodium aluminate (43 wt% solution), 27.6 grams of 1-heptylamine, 17.9 grams of sodium hydroxide (50 wt% solution), and 672 grams The water is mixed together. The gel crystallized at 180°C for 18 hours.

The crystalline product was filtered, washed with deionized water and dried in air. The zeolite powder was calcined at 550°C for 6 hours to remove organic molecules from the pores.

The product was analyzed by powder XRD and showed pure phase ZSM-5 (MFI). The zeolite has a SAR of 50. The crystal size was analyzed by SEM and the average crystal size was shown to be 4.4 microns. Zeolite G

Mix 709 grams of colloidal silica (Nyacol, 40 wt% SiO ₂ ), 36.6 grams of sodium aluminate (43 wt% solution), 30.5 grams of 1-octylamine, 17.6 grams of sodium hydroxide (50 wt% solution), and 661 grams The water is mixed together. The gel crystallized at 180°C for 18 hours.

The crystalline product was filtered, washed with deionized water and dried in air. The zeolite powder was calcined at 550°C for 6 hours to remove organic molecules from the pores.

The product was analyzed by powder XRD and showed pure phase ZSM-5 (MFI). The zeolite has a SAR of 50. The crystal size was analyzed by SEM and the average crystal size showed 4.0 microns. Zeolite H

Mix 709 g colloidal silica (Nyacol, 40 wt% SiO ₂ ), 36.2 g sodium aluminate (43 wt% solution), 23.6 g dipropylamine, 17.4 g sodium hydroxide (50 wt% solution) and 653 g water Together. The gel crystallized at 180°C for 18 hours.

The crystalline product was filtered, washed with deionized water and dried in air. The zeolite powder was calcined at 550°C for 6 hours to remove organic molecules from the pores.

The product was analyzed by powder XRD and showed pure phase ZSM-5 (MFI). The zeolite has a SAR of 47. The crystal size was analyzed by SEM and the average crystal size was shown to be 2.6 microns. Catalyst preparation

Catalysts A-H were prepared from zeolite samples A-H by mixing ZSM-5 zeolite with silica as a binder, kneading and extruding to form a shaped support and then impregnating with metal hydride by pore volume impregnation. Each carrier contains 60 wt% zeolite combined with 40 wt% silica binder (approximately 2:1 weight ratio is a mixture of "Sipernat 50" from Evonik and "Bindzil 30NH3" silica sol from Nouryon) . The extrudates were calcined at 500°C and impregnated with a Pt solution so that the final catalysts each had a composition containing 0.02 wt% Pt.

Catalyst I was prepared by mixing, kneading and extruding 60 wt% commercial ZSM-5 CBV 5524G (Zeolyst, SAR 50) zeolite and 40 wt% silica binder (approximately 2:1 weight ratio derived from A mixture of "Sipernat 50" from Evonik and "Bindzil 30NH3" silica sol from Nouryon). The extrudate was calcined at 500°C. The calcined extrudate was treated with a 0.03 M ammonium hexafluorosilicate (AHS) solution, and then impregnated with a Pt solution, so that the final catalyst had a composition containing 0.02 wt% Pt.

The catalyst JQ was prepared by mixing, kneading and extruding 60 wt% ZSM-5 zeolite (zeolite AH respectively) and 40 wt% silica binder (approximately 2:1 weight ratio from Evonik "Sipernat 50" and "Bindzil 30NH3" silica sol from Nouryon). The extrudate was calcined at 500°C. The calcined extrudate was treated with 0.03 M ammonium hexafluorosilicate (AHS) solution, and then impregnated with Pt solution, so that the final catalyst had a composition containing 0.02 wt% Pt.

Table 1 below summarizes the prepared catalysts. Table 1 Catalyst name Zeolite Zeolite name Templating agent used Treated with 0.03 M AHS*** SAR Average crystal size μm) BET total surface area (m ² /g)**** A (comparison) A (comparison) TPABr*/TMACl** no 62 2.3 432 B (comparison) B (comparison) TPABr* no 51 0.8 443 C C 1-butylamine no 55 2.9 462 D D 1-pentylamine no 50 2.3 434 E E 1-hexylamine no 49 3.8 421 F F 1-heptylamine no 50 4.4 436 G G 1-octylamine no 50 4.0 418 H H Dipropylamine no 47 2.6 424 I (comparison) I (comparison) Not yet revealed Yes 50 0.2 425 J (comparison) A (comparison) TPABr*/TMACl** Yes 62 2.3 432 K (comparison) B (comparison) TPABr* Yes 51 0.8 443 L C 1-butylamine Yes 55 2.9 462 M D 1-pentylamine Yes 50 2.3 434 N E 1-hexylamine Yes 49 3.8 421 O F 1-heptylamine Yes 50 4.4 436 P G 1-octylamine Yes 50 4.0 418 Q H Dipropylamine Yes 47 2.6 424 * Tetrapropylammonium bromide (TPA). ** Tetramethylammonium chloride (TMA). *** Treat the zeolite with 0.03 M ammonium hexafluorosilicate (AHS) solution. **** As measured by ASTM D4365-95. Catalyst test

The catalyst is subjected to a catalytic test, which simulates typical industrial application conditions for ethylbenzene dealkylation in a fixed bed reactor unit. The activity test uses feeds that are representative of feeds commonly used in industrial units. The composition of the feed used for the test is summarized in Table 2. Table 2 Composition of feed materials used for activity test Feed composition EB wt% 13.1 pX wt% 3.7 oX wt% 17.8 mX wt% 63.8 Toluene wt% ＜0.1 benzene wt% ＜0.01 C ₇ -C ₉ alkanes wt% 1.5 C ₉₊ aromatics wt% ＜0.1 total wt% 100.00 C ₈ aromatics sum EB in C _{8 aromatic feed} wt% 13.3 PX in xylene in feed wt% 3.8 OX in xylene in the feed wt% 18.1 MX in xylene in feed wt% 64.8

Once the catalyst is in its reduced state, the activity test is carried out in a fixed bed unit with on-line GC analysis. The reduced state consists of exposing the dried and calcined catalyst to atmospheric hydrogen (>99% purity) at 450°C for 1 hour Come to reach.

After the reduction, the reactor was cooled to 380°C, pressurized to 1.2 MPa, and the feed was introduced at a weight space rate of 12 g feed/g catalyst/hour and a hydrogen to feed ratio of ^{2.5 mol.mol -1} . Subsequently, the temperature was increased to 450° C., and the weight space rate was reduced to 10 g feed/g catalyst/hour, and the ratio of hydrogen to feed was reduced to 1 mol.mol ^-1 . This step contributes to enhanced catalyst aging and therefore allows for more stable operation of the catalytic performance. After 24 hours, the conditions were changed to actual operating conditions.

In the current situation, a weight space velocity of ^{12 hours- 1} , a hydrogen to feed ratio of 2.5 mol.mol -1 and a total system pressure of 1.3 MPa are used. The temperature is varied between 340 and 380°C to achieve the desired conversion rate that is easier to compare.

The performance characteristics evaluated in this test are as follows:

Ethylbenzene conversion rate (EB conversion rate) is the weight percentage of ethylbenzene converted into benzene and ethylene or other molecules by a catalyst. It is defined as the ethylbenzene wt.% in the feed minus the ethylbenzene wt.% in the product divided by the ethylbenzene wt.% in the feed multiplied by 100%.

_{The formation of C 9} aromatic components such as trimethylbenzene (TMB) is undesirable because it is formed at the expense of better products such as p-xylene and benzene. result

Table 3 below shows the performance of the catalyst at a conversion rate of 65% ethylbenzene (EB). table 3 catalyst Zeolite EB conversion rate (wt%) Reactor temperature (℃) TMB formation (wt%) A (comparison) A (comparison) 65 375 0.456 B (comparison) B (comparison) 65 362 0.777 C C 65 358 0.305 D D 65 364 0.383 E E 65 362 0.349 F F 65 361 0.267 G G 65 363 0.264 H H 65 356 0.222 I (comparison) I* (comparison) 65 376 0.725 J (comparison) A* (comparison) 65 371 0.366 K (comparison) B* (comparison) 65 362 0.560 L C* 65 360 0.234 M D* 65 363 0.274 N E* 65 360 0.219 O F* 65 361 0.168 P G* 65 360 0.144 Q H* 65 355 0.208

*The zeolite is treated with 0.03 M AHS.

According to the data in Table 3, it is clear that the catalyst CH prepared from ZSM-5 zeolite synthesized with primary and secondary amine templates of different lengths exhibits better performance than similar catalysts containing comparable TPA templates or commercial zeolite at the same EB conversion rate (compare Catalysts A, B and I) significantly lower TMB formation.

Table 3 shows that although for the comparative catalysts containing TPA template zeolite (comparative catalysts A and B), TMB formation can be improved by additionally selectively treating zeolites A and B with AHS (comparative catalysts J and K) (ie Further reduction), but the resulting TMB formation of the treated comparative catalysts J and K is generally still greater than that of the untreated catalyst CG.

Therefore, the catalyst of the present invention allows beneficial reduction of TMB formation without the need for additional catalyst treatment.

However, it is also obvious in Table 3 that the selective treatment of zeolite C-H with AHS resulted in a further synergistic improvement in the reduction of TMB formation. The catalyst L-Q according to the present invention exhibits particularly effective selectivity (that is, increased catalyst activity) in combination with a lower temperature to achieve 65% EB conversion.

without

without

Claims (11)

An ethylbenzene dealkylation catalyst composition comprising ZSM-5 type zeolite as a carrier component, wherein the zeolite is composed of one or more alumina sources, one or more silica sources, one or more alkali sources, and one or more Synthesis of an aqueous reaction mixture of primary and/or secondary amines, and wherein the ZSM-5 type zeolite has a number average crystallite size in the range of 1 to 10 µm and a mole of silica and alumina in the range of 30 to 70 Ratio (SAR). The catalyst composition of claim 1, wherein the one or more amines are primary and/or secondary amines ^{having the formula R 1} NH ₂ and/or R ² R ^{3 NH, wherein one of R 1} , R ² , and R ³ Each is independently selected from alkyl groups having 3 to 8 carbon atoms, and wherein R ² and R ³ may be the same or different. The catalyst composition of claim 1 or 2, wherein the one or more amines are primary and/or secondary amines ^{having the formula R 1} NH ₂ and/or R ² R ^{3 NH, wherein R 1} , R ² , R ³ Each of them is independently selected from linear alkyl groups having 3 to 8 carbon atoms, and wherein R ² and R ³ may be the same or different. The catalyst composition of any one of claims 1 to 3, wherein the one or more sources of silica are selected from silica sol, silica gel, silica aerogel, silica hydrogel , Silicic acid, silicate and sodium silicate. The catalyst composition according to any one of claims 1 to 4, wherein the ZSM-5 type zeolite has a number average crystallite size in the range of 1 to 7 µm. The catalyst composition according to any one of claims 1 to 5, wherein the ZSM-5 type zeolite has a molar ratio (SAR) of silica to alumina in the range of 45 to 70. The catalyst composition according to any one of claims 1 to 6, wherein the composition further comprises one or more metals and one or more inorganic oxide binders. The catalyst composition of claim 7, wherein the one or more metals are selected from ruthenium, rhenium, iron, chromium, molybdenum, tungsten, palladium, platinum, tin, lead, silver, copper and nickel. The catalyst composition according to any one of claims 1 to 8, wherein the carrier containing the ZSM-5 type zeolite as a carrier component is dealuminated. A method for reducing the loss of xylene in an ethylbenzene dealkylation process, the method comprising performing the ethylbenzene dealkylation process in the presence of the catalyst composition according to any one of claims 1 to 9. A process for the dealkylation of ethylbenzene, the process comprising contacting a raw material containing ethylbenzene with a catalyst composition according to any one of claims 1 to 9 in the presence of hydrogen.